<i>Z</i>-Isomers of Astaxanthin Exhibit Greater Bioavailability and Tissue Accumulation Efficiency than the All-<i>E</i>-Isomer

Abstract

The purpose of the present study was to clarify the differences in the bioavailability and tissue accumulation efficiency between (all-<i>E</i>)- and (<i>Z</i>)-astaxanthin. Astaxanthin with a high proportion of the <i>Z</i>-isomer (especially rich in the 9<i>Z</i>- and 13<i>Z</i>-isomers) was prepared from (all-<i>E</i>)-astaxanthin by thermal treatment and solid-liquid separation. The all-<i>E</i>-isomer- or <i>Z</i>-isomer-rich diet was fed to male rats for 2 weeks. After the feeding period, blood and tissue samples were collected, and their astaxanthin levels were evaluated. The <i>Z</i>-isomer-rich astaxanthin diet resulted in higher levels of astaxanthin in blood and many tissues (in particular, skin, lung, prostate, and eye) compared to the all-<i>E</i>-isomer-rich diet. Moreover, the <i>Z</i>-isomer-rich diet enhanced the level of the 13<i>Z</i>-isomer in blood and tissues rather than that of the 9<i>Z</i>-isomer. These results strongly supported that astaxanthin <i>Z</i>-isomers have greater bioavailability and tissue accumulation efficiency than the all-<i>E</i>-isomer. Moreover, (13<i>Z</i>)-astaxanthin would have higher bioavailability and tissue accumulation than the other isomers.